The present invention relates a method of controlling a valve of an injector for supplying fuel to an engine, and more particularly to a method of controlling a valve driving operation of the injector using a stacked piezoelectric ceramics.
Conventionally, in a fuel injector including a stacked piezoelectric ceramics for reciprocating a valve and controlling an amount of fuel to be injected to the engine, a pulse signal is supplied to the stacked piezoelectric ceramics to lift the valve against a biasing force of a spring, and the supply of the pulse signal is cut to return the valve to its closed position by the biasing force of the spring. In the conventional injector, a pulse width in each pulse rate as shown in FIG. 1A is changed to vary a fuel flow rate in a linear range between Q1 and Q2 as shown in FIG. 2.
However, even when a rectangular pulse waveform as shown in FIG. 1A is supplied to the piezoelectric ceramics, a waveform of a valve stroke is disturbed at the stroke end as shown in FIG. 1B because the valve bounds at the stroke end. Therefore, the linear range between Q1 and Q2 in FIG. 2 is shortened to reduce a flow control range, thereby causing reduction in engine operational characteristics. Further, at the end of the valve opening stroke, the valve strongly collides with the stopper by the driving force of the stacked piezoelectric ceramics, while at the end of the valve closing stroke, the valve strongly collides with the valve seat by the biasing force of the spring. As a result, a valve operational noise is generated from the injector upon bounding of the valve, and life of the valve is shortened.